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Med Phys. 2018 Jul;45(7):3466-3474. doi: 10.1002/mp.12988. Epub 2018 Jun 8.

Temporally feathered intensity-modulated radiation therapy: A planning technique to reduce normal tissue toxicity.

Author information

1
Department of Systems Immunology and Braunschweig Integrated Centre of Systems Biology, Helmholtz Centre for Infection Research, Rebenring 56, Braunschweig, 38106, Germany.
2
Department of Radiation Oncology, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, 44195, USA.
3
Department of Radiation Oncology, Moffitt Cancer Center, 12902 USF Magnolia Drive, Tampa, FL, 33612, USA.
4
Department of Radiation Oncology, MD Anderson Cancer Center, 1840 Old Spanish Trail, Houston, TX, 77054, USA.
5
Department of Integrated Mathematical Oncology, Moffitt Cancer Center, 12902 USF Magnolia Drive, Tampa, FL, 33612, USA.
6
Department of Translational Hematology and Oncology Research, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH, 44195, USA.

Abstract

PURPOSE:

Intensity-modulated radiation therapy (IMRT) has allowed optimization of three-dimensional spatial radiation dose distributions permitting target coverage while reducing normal tissue toxicity. However, radiation-induced normal tissue toxicity is a major contributor to patients' quality of life and often a dose-limiting factor in the definitive treatment of cancer with radiation therapy. We propose the next logical step in the evolution of IMRT using canonical radiobiological principles, optimizing the temporal dimension through which radiation therapy is delivered to further reduce radiation-induced toxicity by increased time for normal tissue recovery. We term this novel treatment planning strategy "temporally feathered radiation therapy" (TFRT).

METHODS:

Temporally feathered radiotherapy plans were generated as a composite of five simulated treatment plans each with altered constraints on particular hypothetical organs at risk (OARs) to be delivered sequentially. For each of these TFRT plans, OARs chosen for feathering receive higher doses while the remaining OARs receive lower doses than the standard fractional dose delivered in a conventional fractionated IMRT plan. Each TFRT plan is delivered a specific weekday, which in effect leads to a higher dose once weekly followed by four lower fractional doses to each temporally feathered OAR. We compared normal tissue toxicity between TFRT and conventional fractionated IMRT plans by using a dynamical mathematical model to describe radiation-induced tissue damage and repair over time.

RESULTS:

Model-based simulations of TFRT demonstrated potential for reduced normal tissue toxicity compared to conventionally planned IMRT. The sequencing of high and low fractional doses delivered to OARs by TFRT plans suggested increased normal tissue recovery, and hence less overall radiation-induced toxicity, despite higher total doses delivered to OARs compared to conventional fractionated IMRT plans. The magnitude of toxicity reduction by TFRT planning was found to depend on the corresponding standard fractional dose of IMRT and organ-specific recovery rate of sublethal radiation-induced damage.

CONCLUSIONS:

TFRT is a novel technique for treatment planning and optimization of therapeutic radiotherapy that considers the nonlinear aspects of normal tissue repair to optimize toxicity profiles. Model-based simulations of TFRT to carefully conceptualized clinical cases have demonstrated potential for radiation-induced toxicity reduction in a previously described dynamical model of normal tissue complication probability (NTCP).

KEYWORDS:

dosimetry planning; normal tissue complication probability; normal tissue toxicity reduction; temporally feathered radiation therapy; therapeutic ratio

PMID:
29786861
PMCID:
PMC6041138
[Available on 2019-07-01]
DOI:
10.1002/mp.12988
[Indexed for MEDLINE]

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